The invention relates to method and apparatus for growing crystals.
Large KDP crystals with high damage threshold are required for the NOVA and future high power lasers at LLNL. The crystals are used for frequency conversion to produce laser wavelengths which may be more optimum to produce laser fusion. Theoretically, a damage threshold of 80 J/cm.sup.2 in 1 ns pulses can be reached. For the next generation laser, 40 J/cm.sup.2 in 10 ns pulses is desired. However, the best crystals presently available, which are annealed, have a damage threshold of 15 J/cm.sup.2 in 10 ns pulses.
Crystals are grown by placing a seed crystal in a crystal growth solution. In general, it is necessary to move the crystal growth solution over the crystal face to promote growth. It is also desirable to have the solution at substantially its saturation temperature when it contacts the crystal face. The motion of the solution over the crystal face is typically produced by a mechanical apparatus which either moves the crystal in the solution or moves the solution over the crystal. The means for producing this relative motion, unfortunately, introduce contaminants, e.g., particulates and organics. Any apparatus with metal parts, motors, and lubricated gears produces contaminants. The crystal growth solution at saturation temperature cannot be filtered to remove the contaminants since it will clog the filter.